The types of chemical warfare agents which are considered to constitute a major threat are those commonly designated as HD, V and G. The first of these, HD, is an acronym for mustard gas, the `D` implying that it is distilled. The formula for this compound is ClCH.sub.2 CH.sub.2 --S--CH.sub.2 CH.sub.2 Cl. It belongs to the vesicant class of chemical warfare agents. V and G stand for the V- and G-series of nerve agents. The G-series tend to be volatile and highly toxic by inhalation, whilst the V-agents are relatively non-volatile, persistent, and highly toxic by the percutaneous route.
Typical examples of these series are GD and VX which have the following formulae: ##STR1##
To be of practical use under field conditions, any cream or lotion which is to be used either for decontamination or as a cream providing protection against chemical warfare agents has to possess certain desirable properties. First, it must be effective against all three of these types of chemical warfare agents. Second, for use as a barrier cream, it must be compatible with human skin and not cause any adverse reactions, at least over a limited period of time. Third, it must provide protection for a reasonable period of time. In this context it is to be noted that "decontamination" includes both coating before exposure to negate effects, and cleaning after exposure to remove potentially lethal deposits. These three criteria effectively exclude many of the currently known decontamination systems which have been devised as a means of destroying chemical warfare agents either for use as barrier creams, or to decontaminate relatively sensitive substances such as fabrics and the like. The chief difficulty is that such decontamination systems contain very powerful reagents which often will damage the surface being treated. Some of these systems are very alkaline, and some use concentrated active chlorine or bleach solutions. Thus, although these systems are, more or less, efficacious as decontaminants for equipment which has been exposed to chemical warfare agents, they are of no use in protecting or decontaminating people, and give no guide at all as to the sort of systems that might be used to formulate protective systems.
One solution to the barrier cream problem has been proposed which permits the formulation of a cream which is effective against all three types of agents, causes minimal adverse skin reactions during the periods of time for which such a barrier cream is likely to be worn, and also provides the wearer with protection for a reasonable period of time.
Although these proposed creams contain a reagent that is potentially extremely basic, for example, potassium phenoxide, they do appear to be compatible with skin.
In detail, these proposed creams provide a barrier cream consisting essentially of at least one active ingredient chosen from the alkali metal salts of mono- and dihydroxy phenols, and alkyl and mono alkoxy substituted mono and dihydroxy phenols, in which the alkyl groups each contain from 1 to 4 carbon atoms, dispersed in a substantially anhydrous state in a base medium comprising a polyethylene glycol which has been partially etherified to reduce the free hydroxyl group content. In these creams the preferred active ingredient is potassium phenoxide.
Similar creams have also been proposed in which the active ingredient is chosen from an alkali metal, preferably potassium, salt of phenol, acetophenone oxime, acetone oxime and 2,3-butanedione monoxime, together with a similar polyethylene glycol base, which also includes a macrocycle chosen from the compounds known as 18-crown-6 and crypt and[2,2,2], and a small amount of water.
Whilst these creams have been found to be effective, in that they meet the three main properties enumerated above reasonably efficiently, they are not without certain disadvantages, for example the macrocycles used are expensive.
These creams contain essentially three components: the reactive substance, which destroys the chemical warfare agent, a macrocycle and the base in which they are dispersed. To prepare these creams, the reactive substance, for example potassium phenoxide and macrocycle have to be prepared first, and then added to the base. These substances are both difficult to prepare and difficult to handle since they are particularly sensitive to reaction with water.
An advantage would be gained, therefore, if the preparation of these creams could be simplified.